We have performed the first measurement of the coherent ψ(2S) photo-production cross section in ultra-peripheral Pb–Pb collisions at the LHC. This charmonium excited state is reconstructed via the ψ(2S)→l+l− and ψ(2S)→J/ψπ+π− decays, where the J/ψ decays into two leptons. The analysis is based on an event sample corresponding to an integrated luminosity of about 22 μb−1. The cross section for coherent ψ (2S) production in the rapidity interval −0.9 < y < 0.9 is dσ coh /d y = 0.83 ± 0.19 stat + syst mb. The ψ (2S) ψ (2S) to J/ψ coherent cross section ratio is 0.34+0.08 (stat + syst). The obtained results are compared to predictions from theoretical models.
Coherent ψ(2S) photo-production in ultra-peripheral PbPb collisions at √sNN = 2.76 TeV
LEA, RAMONA;RUI, RINALDO;
2015-01-01
Abstract
We have performed the first measurement of the coherent ψ(2S) photo-production cross section in ultra-peripheral Pb–Pb collisions at the LHC. This charmonium excited state is reconstructed via the ψ(2S)→l+l− and ψ(2S)→J/ψπ+π− decays, where the J/ψ decays into two leptons. The analysis is based on an event sample corresponding to an integrated luminosity of about 22 μb−1. The cross section for coherent ψ (2S) production in the rapidity interval −0.9 < y < 0.9 is dσ coh /d y = 0.83 ± 0.19 stat + syst mb. The ψ (2S) ψ (2S) to J/ψ coherent cross section ratio is 0.34+0.08 (stat + syst). The obtained results are compared to predictions from theoretical models.File | Dimensione | Formato | |
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